Gas sampling devices are used in many applications such as, for example, in the natural gas industry where they are used on pipelines, storage vessels, and gas processing equipment. These gas sampling devices have the primary function of removing any entrained liquids and particle contaminants from the gas stream and regulating the flow rate of the gas into a gas analyzer that measures some property of the gas. In the natural gas industry, the analyzers are often measuring water vapor, oxygen, hydrogen sulfide or other gas contaminants in the natural gas.
Conventional gas sampling devices use multiple components such as valves, flow meters, liquid separators, and filters that are joined and sealed together by tubing, threaded joints, and compression fittings. These devices are constantly subject to possible leakage at the locations where the joints or fittings are poorly sealed. In the typical arrangement there are ten or more fittings that could leak at either the compression side or the threaded side. In addition, the tubing results in the creation of lengthy, inefficient gas flow paths that have a high surface area and often include dead spaces. In the typical arrangement there is about four feet of tubing connecting the components. Liquids and other contaminants, especially water and hydrogen sulfide, tend to stick to those surfaces and collect in the dead spaces where there is insufficient flow to keep them entrained. Liquids that are collected in the pipes and tubing will not reach the analyzer for measurement. The collected liquids and/or contaminants on the surfaces and in the dead spaces can unexpectedly and unwantedly diffuse into the gas stream over time and produce false readings in the analyzer. As a specific example of this, during colder times of the day some of the water vapor may adsorb onto the pipes and tubing and the analyzer will read a lower value for water vapor in the gas. At warmer times this adsorbed water vapor may be released into the gas stream and give a higher reading. Therefore, it is desirable to minimize the surface area and dead zones in the gas sampling device.